1. Field of the Invention
The present invention relates to a signal transmission system, and more particularly, to a signal transmission system of a flat panel device.
2. Description of the Prior Art
The traditional flat panel device includes a timing controller and a plurality of source drivers. The timing controller generates display data of the flat display after receiving image signals. The display data is transmitted to the plurality of source drivers through transmission interface. The plurality of source drivers converts the display data to driving signals so as to display the image on the flat panel device. In general, the transmission interface of the flat panel device includes transistor-transistor logic (TTL) signal, low voltage differential signal (LVDS), and reduced swing differential signal (RSDS).
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram of circuits generating RSDS signals according to the prior art. FIG. 2 is a waveform diagram of RSDS signals. For the RSDS generation, when a current I passes through a terminal resistor R, a voltage difference I*R is generated between two ends (RSDS_P, RSDS_N) of the terminal resistor. The system includes a common mode voltage (VCM_RSDS). The voltages of two ends of the terminal resistor (VRSDS_P, VRSDS_N) have voltage difference 0.5*I*R to the common mode voltage (VCM_RSDS) so as to generate stable differential signals. As shown in FIG. 1, when the current flows from RSDS_P to RSDS_N, VRSDS_P is VCM_RSDS+0.5*I*R, and VRSDS_N is VCM_RSDS−0.5*I*R, which is defined as a high level. When the current flows in the reverse direction, VRSDS_P is VCM_RSDS−0.5*I*R, and VRSDS_N is VCM_RSDS+0.5*I*R, which is defined as low level. As shown in FIG. 2, VIH_RSDS is defined that the voltage at RSDS_P is I*R higher than at RSDS_N, and VIL_RSDS is defined that the voltage at RSDS_N is I*R higher than at RSDS_P.
In conclusion, the RSDS according to the prior art uses one pair of differential signals to transmit data. However, as the resolution of the display increases the transmission interface of the RSDS has to transmit a lot of data, so one pair of differential signals is insufficient.